Motor-controller.



C. T. HENDERSON MOTOR CONTROLLER.

APPLICATION FILED MAR. 6, 1914.

1 1 96,778. Patented Sept. 5, 1916.

UNITED STATES PATE T oFFIoE.

CLARK T. HENDERSON, MILWAUKEE, WISCONSIN, ASSIGNOB TO THE CUTLER- HAMMER MFG. 00., OF MILWAUKEE, WISCONSIN, A CORPQRATION OF WIS- CONSIN.

MOTOR-CONTROLLER.

. ing, forming a part of this specification.

This trollers.

The various objects and advantages of the invention will'be apparent from the embodi- 5 ment thereof diagrammatically illustrated invention relates to motor conin the. accompanying drawing and now to p be described. v

Referring to the drawing, the same shows a shunt motor 1 having an armature A and a shunt field winding F. It also shows a conventional form of adjustable field rheostat 2 for regulating the speed of the motor, and two relay switches 3 and 4 coacting with saidrheostat to automatically regulate the 5 field strength of the motor, as hereinafter set forth. 7 1 l The rheostat 2 is shown as comprising a pivoted arm 5 movable over a series of contacts 6 to vary a resistance 1'. When in the position illustrated the arm short-circuits all of the resistance 1' from the field circuit of the motor and when moved to the right gradually inserts said resistance in said circuit. 1

' The relay switch 3 is normally open and 7 controls a short circuit aroundthat portion of the resistance 1' included in circuit by the rheostat arm 5 when moved to the right. This switch has a winding 3 in series with the motor armature and an auxiliary Winding 3 connected across the lines. During the acceleration of the motor these two wind- -ings act cumulatively to effect closure of the switch 3 whenever the armature ourrent exceeds a predetermined value. Closure. of the switch 3 in turn short-circuits the resistanceir included in the field circuit, thereby strengthening the motor field and effecting a reduction in the armature ourrent. The relay 3 vibrates, alternately ex- Specification of Letters Patent.

Patented se a 5, 1916.

Application filed March 0, 1914. Serial No. 822,862.

removal of the field resistance by the rheo- I stat arm. When, however, as often occurs .in deceleration, the motor acts as a genera tor to return power to the lines, the two windings of the'relay act in opposition to insure against response of the relay.

The provision of the two windings for the relay 3 is important and extremelyadvam tageous for the following reasons: When the motor acts as a generator it frequently occurs that the current generated thereby attains or exceeds the value at which the relay 3 is set to respond in acceleration. Accordingly should the relay be free to respond then it would short-circuit the field 7o resistance, increasing the field strength and augmenting the current delivered by the armature. This would. be extremely undesirable since the motor requires substantially the same protection against excessive current when acting as a generator as when operating upon power from the lines and the effect of the relay would be just the op- I posite of that desired. Provision of the two windings as aforesaid, however, posio tively insures against operation of the relay, and in so doing overcomes the difiiculties discussed.

As before stated, the motor requires pro tection when acting as a generator and it .is to afford such protection that the re lay switch 4 is provided. This switch is normally closed to complete a short-circuit around that portion of the resistance to the right of the rheostat arm 5. It is provided with two windings 4 and 4 which oppose one another when the motor operates upon power from the lines and which act cumulatively when the motor acts as a generator. Accordingly these windings function just the reverse of those of relay 3, whereby said switch 4 is rendered ineffective during acceleration. When, however; the motor acts as a generator and the current delivered thereby exceeds a certain value the two windings act together to open the relay switch 4 to insert in the field circuit that portion of the resistance short-circuited by the rheostat arm. This, in turn, decreases the field strength of the machine and there- 106 by effects a reduction of the current delivered by the armature and so long as the current generated tends to exceed the predetermined value the relay switch 4 vibrates similarly to the relay 3 to protect 110 innards themotor. Thus the means illustrated'Pro vides for equal protection of the motor under running and generating conditionsall danger ofinterference between the a protective means is eliminated by the du-.

:ductor 7 through the motor armature A, by

conductor 8 throughthe winding 3 of relay 3, by conductor 9 through winding t fof F relay 4, by conductor 10 to line L; This provides for series connection of the motor armatureand the relay windings 8 and'i.

- A second circuit extends from conductor 7 by conductor 11 through the. winding 3* of relay 3, by conductor 12 through the winding 4* of relay 4, by conductor 13 to conductor 10. This provides for connection of the two windings 3 and 43 in series across the. lines; i

A- third circuit extends from line L by I conductor llthrough the motor field winding Rby conductor. 15 through resistance r, by conductor 16 toline L. I y 2, however, is connected by conductor 17.

through relay switch 1, by conductor '18 to" conductor 16, whereby said rheostat arm may be moved to short circuit all or any desired part of the resistance "1' from the field circuit.

At the same time these connections provide for inclusion of all of the resistance r in the.

field circuit when the switch 4 opens.

The remaining circuit extends from conductor 15 by conductor 19 through switch 3 to conductor 17 and rheostat arm 2, and, as

is apparent, this circuit when completed short-circuits all of the resistance r to the left of the rheostat arm, or in other words, that portion of the resistance included in the field circuit by said rheostat arm.

With the circuit connections just described it will be apparent that the direction of flow of current through the relay windings 3 and 4:" will always be the same while the flow of current through the windings 3* and 4, will be subjectto reversal when the motor acts as a generator. Thus is effected the aforesaid changes in the coaction of said windings.

W hat I claim as new and desire to secure by Letters Patent is:

1. in a motor controller, in combination, a field resistance, means for removing said re sistance from circuit in steps and a. current relay responsive to reinsert in circuit the steps of said resistance excluded by said means.

2. in a controller for electric motors, in combination, a field resistance, means for incombination, eluding and excluding sa1d resistance in The rheostat arm eluding and excluding said resistance in sections, means operable automatically to ex-- elude from circuit that portion of said resistance included in circuit by said first-mentioned means,'and other means operable au tomatically to include in circuit that portion of said resistance excluded by said first men-- tioned means.

1 3. In a controller for electric motors, in

' combination, a field resistance, means for includmg and excluding sa1d resistance 1n steps, a switch operable to exclude that portion of theresistance included by said means, another switch operable to include that portion of said resistance excluded by said means, and means for automatically operating said switches under different conditions and rendering each inoperative under operative conditions of the other.

4. In a controller for electric motors,'in a field resistance, means for in steps, aswitch operable to exclude that'portion of the resistance included by said means, another switch operable-to include that portion of said resistance excluded by said means, and'eleotro-responsive means for operating'said switches under different condltions and insuring against operation of each upon operation of the other.

5. In a controller for electric motors, in combination, a resistance, a switch operable to exclude said, resistance from circuit, a

switch operable to include said resistance in circuit, and a plurality of windings fior each of said switches, the windings of each switch acting cumulatively and in opp0si-' tion under different conditions, and connections for said windings insuring reverse actions of the windings of said switches under all conditions. I

6. In combination, an electric motor, a field resistance therefor, and means responsive. to the current supplied to said motor to exclude said resistance from circuit, said means having associated therewith means to insure against its operation when said motor acts as a generator.

7. The combination with an electric motor, of a field resistance therefor, and a relay switch controlling said resistance, said switch having a winding in series with the motor armature and an independently excited winding, said windings acting cumulatively during operation of said motor upon power supplied from the lines and acting in opposition when said motor acts as a generator.

8. Tn a controller for electric motors, in

combination, a field resistance, a relay oper able to'exclude said resistance from circuit,

a relay operable to include said resistance in circuit, each of said relays having two windings and connections for subjecting one winding of each of said relays to the armature current and for independently energizing the other winding oteach relay, whereby the windings of each relay may act either cumulatively or in opposition and are in- 'sured a reverse action to that of the windings of the other relay.

9. In combination, a source of power, a motor to operate upon power from said source and under certain conditions to act as a generator to reverse the flow of current in its armature circuit, a field resistance, two relays, one operable to include and the other operable to'exclude said resistance for limiting the armature current to a predetermined value during acceleration and deceleration, and electro-responsive means to operate said relays selectively in accordance with the direction of flow of the armature current.

10. In combination, a source of power of substantially constant potential, a motor supplied with power therefrom, afield resist ance, means for increasing said field resistance for acceleration of said motor and decreaslng said resistance for deceleration operative during deceleration and said third mentioned means being inoperative during acceleration. a

In witness whereof, I have hereunto subscribed my name in thepresence of two witnesses.

CLARK T. HENDERSON.

Witnesses:

L. F. WATSON, LEHLA Bnsr. 

